Cardiovascular diseases have since become the number one fatality in western industrial nations with ishemic heart disease and heart failure being the most frequent causes of death in Germany. Of a total of 2.7 million in in-patient treatment for cardiovascular diseases, roughly 15% die.
Implantable mechanical ventricular assist devices (VAD) have been in use now clinically for some 15 years. This form of therapy mainly serves as a bridge to transplant when no donor organ is available or the patient is already in such a critical health condition that he would in all probability fail to survive the acute stress of a heart transplantation and the initial high-dosis immune suppressive therapy involved. Then, following stabilization over several months by a VAD with an improvement in the organ functions detrimented previously by acute or chronic diminished circulation, the patients can be admitted to heart transplantation with a higher anticipated success.
More recent results have shown that the functioning of the heart may be improved by this therapy to such an extent that there is a possibility of system explantation without a subsequent heart transplantation (bridge to recovery). A future aim with assist systems of enhanced reliability is to allow them to remain in the body as an alternative to transplant (ATT).
Due to the lack of donors and organ allocation in accordance with a waiting list early or, in some cases, premature application for transplantation is experienced which results in suboptimal organ allocation. By making use of suitable heart assist systems on a full-scale basis available donor organs could be optimally allocated by eliminating a waiting time calculation and the result of the heart transplantation could be improved on recovery of the organ functioning following mechanical ventricular assistance.
Since no fully implantable, biventricular assist system is hitherto available, only extracorporal systems for assisting biventricular failure could hitherto find application. Left ventricular assist systems are built as a rule with a pump chamber.
Currently, the only way of assisting both ventricles is with a total artificial heart (TAH) which, however, is too big to be additionally implanted as an assist system. Instead, the native heart in this case would have to be totally removed, resulting in no back-up being available should the artificial system fail. This therapy also eliminates the bridge to recovery (BTR) option since the heart has been removed. Experience has furthermore shown that it is easier to make the transplantation when the patient had the supply of an assist system than when a total artificial heart (TAH) was implanted.
Problematic in a biventricular assist is making the connection to the right ventricle because of its thin muscle tissue. Hitherto this connection was made via anastomosis to the right atrium. Since the tissue here too is relatively thin, haemorrhage complications may arise should the suture rupture. On top of this, there is the danger of the atrium collapsing on blood intake due to an assist system.